Executive power is exercised by ministers, all of whom are sworn into the Executive Council and accountable to the elected legislature, the House of Representatives.[11] Several senior ministers (usually 20[12]) constitute a collective decision-making body known as Cabinet, which is led by the prime minister (currently Jacinda Ardern). A few more ministers (usually junior or supporting) are part of the Executive Council but outside Cabinet. Most ministers have a portfolio of specific responsibilities such as departments or policy areas, although ministers without portfolio are sometimes appointed.

The position of prime minister belongs to the person who commands the support of a majority of members in the House of Representatives. The position is determined also by several other factors, such as support agreements between parties and internal leadership votes in the party that leads the Government. The prime minister and other ministers are formally appointed by the governor-general (who is the Queen's representative in New Zealand).[11] Conventionally, the governor-general acts on the advice of the prime minister in appointing ministers.

The Executive Wing of Parliament Buildings, commonly called the "Beehive" because of the building's shape, houses many government offices and is also where the Cabinet meets.[18] Thus the name Beehive is sometimes used metonymically to refer to the New Zealand Government.[19]

The Queen rarely personally exercises her executive powers; since the sovereign does not normally reside in New Zealand, she appoints a governor-general to represent her and exercise most of her powers.[38] The person who fills this role is selected on the advice of the prime minister.[38] "Advice" in this sense is a choice generally without options since it would be highly unconventional for the prime minister's advice to be overlooked—a convention that protects the monarchy. As long as the monarch is following the advice of her ministers, she is not held personally responsible for the decisions of the Government. The governor-general has no official term limit, and is said to serve "at Her Majesty's pleasure".[39]

As per the conventional stipulations of constitutional monarchy, the Queen and her representative rarely intervene directly in political affairs.[38] Just as the sovereign's choice of governor-general is on the prime minister's advice, the governor-general exercises the executive powers of state on the advice of ministers.[11] For example, the governor-general's power to withhold the Royal Assent to Bills has been rendered ineffective by convention.[35]

Chart showing the relationship between the executive Government and the Parliament. All ministers are MPs.

Under the conventions of the Westminster system, the Government is responsible to the House of Representatives, the democratically elected component of Parliament, rather than to the sovereign. This is called responsible government.[13][14] For example, ministers make statements in the House and take questions from other members of the House.[40] The Government is required by convention and for practical reasons to maintain the support, or confidence, of the House of Representatives. It also requires the support of the House for the maintenance of supply (by voting through the government's budgets) and in order to pass primary legislation.[41][42] By convention, if a government loses the confidence of the House then it must either resign or a general election is held.[14][43] Not since 1928 has a government been defeated on a confidence vote and therefore been obliged to resign.[44]

Upon the dissolution of Parliament, which must occur at least every three years, ministers are no longer members of the House of Representatives; however, they can remain members of the Executive Council for up to thirty days after leaving the House.[11]

Also known as "ministers of the Crown", these are members of Parliament who hold ministerial warrants from the Crown to perform certain functions of government. This includes formulating and implementing policies and advising the governor-general.[45] Before 1996 nearly all ministers were members of the Cabinet, but since the introduction of proportional representation, which has led to complex governing arrangements, there are currently three categories of minister: ministers in Cabinet, ministers outside Cabinet, and ministers from supporting parties.[46]

The Executive Council is a formal body established by the Letters Patent 1983 which exists and meets to give legal effect to decisions made by the Cabinet, and to carry out various other functions. All ministers are members of the Executive Council and are entitled to be styled "The Honourable" for life,[47] except for the prime minister, who is styled "The Right Honourable", a privilege they retain for life.[48] Although not a member of the Executive Council, the governor-general usually presides at Council meetings.[49]

Cabinet (Māori: Te Rūnanga) is the senior collective decision-making body of the Government.[50][51] Constitutional law, such as the Constitution Act 1986, does not recognise the Cabinet as a legal entity; it exists solely by constitutional convention.[52] Its decisions do not in and of themselves have legal force. However, it serves as the practical expression of the Executive Council, which is New Zealand's highest formal governmental body.[45]

The prime minister is responsible for chairing meetings of Cabinet.[25] The governor-general will appoint as prime minister the person most likely to receive the confidence of the House of Representatives to lead the Government. In practice, the appointment is determined by size of each political party, support agreements between parties, and leadership votes in the party that leads the Government.[25][53]

Other ministers are appointed by the governor-general on the advice of the prime minister. Each minister is responsible for the general administration of at least one portfolio, and heads a corresponding public service department (see below).[51][54] The most important minister, following the prime minister, is the finance minister, while other high-profile portfolios include foreign affairs, justice, health and education.

The legislative agenda of Parliament is determined by the Cabinet. At the start of each new parliamentary term, the governor-general gives an address prepared by the Cabinet that outlines the Government's policy and legislative proposals.[55]

Since the introduction of the mixed-member proportional electoral system in 1993[56] governments have been formed following agreements between a large party and smaller support parties. Government ministers from the support parties are often ministers outside Cabinet. Processes were developed to allow the parties to "agree to disagree" on some issues.[57] Ministers outside the Cabinet have the same overall duties and responsibilities as their senior colleagues inside Cabinet.[51][12]

There are two main tiers of elected local authorities—regional councils and territorial authorities—in some places merged into unitary authorities. While the central government deals with issues relevant to New Zealand and its people as a nation, local government exists "to enable democratic local decision-making and action by, and on behalf of, communities", and "to meet the current and future needs of communities for good-quality local infrastructure, local public services, and performance of regulatory functions in a way that is most cost-effective for households and businesses."[63]

There have been three distinctly different periods of New Zealand government—firstly, the period before responsible government; second, from 1856 to 1890, the period in which responsible government begins; and the third period starting with the formation of political parties in 1891.[64]

By convention, a distinct government is named for the largest party that leads it.[65][66][67]

^Wilson, John (8 February 2005). "History – Liberal to Labour". Te Ara: The Encyclopedia of New Zealand. Archived from the original on 27 April 2017. Retrieved 30 April 2017. The watershed election of 1890 put the Liberals, who were to become New Zealand’s first ‘modern’ political party, into power.